This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A015866 #37 Feb 10 2024 11:35:24 %S A015866 20,155,182,184,203,264,621,650,702,852,893,944,1343,1357,2024,2544, %T A015866 2990,4130,4183,4450,5428,5835,6149,6313,6572,8177,8695,11208,11333, %U A015866 11991,12444,12561,12859,13595,14857,16815,18203,18330,18430,19089 %N A015866 Numbers k such that sigma(k) = sigma(k+6). %C A015866 Up to 10^13, sigma(k-6) = sigma(k) = sigma(k+6) only for k = 33227, 604453 and 4223105512993. - _Giovanni Resta_, Mar 03 2014 %D A015866 J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 20, pp 7, Ellipses, Paris 2008. %H A015866 Giovanni Resta, <a href="/A015866/b015866.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Donovan Johnson) %H A015866 A. Weingartner, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL14/Weingartner/wein3.html">On the Solutions of sigma(n) = sigma(n+k)</a>, Journal of Integer Sequences, Vol. 14 (2011), #11.5.5. %t A015866 Select[Range[20000], DivisorSigma[1, #]==DivisorSigma[1, # + 6] &] (* _Vincenzo Librandi_, Mar 10 2014 *) %o A015866 (PARI) is(n)=sigma(n)==sigma(n+6) \\ _Charles R Greathouse IV_, Mar 09 2014 %Y A015866 Cf. A002961, A007373, A015861, A015863, A015865, A015867, A015876, A015877, A015880, A015881, A015882, A015883, A181647. %K A015866 nonn %O A015866 1,1 %A A015866 _Robert G. Wilson v_